Two-layer optical disk

ABSTRACT

A two-layer optical disk has a first layer of a disk shaped recording medium for storing data and a second layer of a disk shaped recording medium placed over the first layer for storing data. Data blocks A, B, C are stored in the first layer in said order. Similarly, data blocks X, Y, Z are stored in the second layer in said order. When reading the data from the two-layer optical disk, the data blocks are read in the order of A, X, B, Y, C, Z.

This application is a division of application Ser. No. 08/666,945, filedJun. 20, 1996, and now is U.S. Pat. No. 5,729,525.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a two-layer optical disk having tworecording layers to which information is recorded, and enablinginformation on both recording layers to be reproduced by irradiating thedisk with light from only one recording layer side.

2. Description of the Prior Art

Optical disks having two data recording layers ("two-layer opticaldisks" below) from which data can be reproduced by irradiating the diskwith light from one side of the disk have been developed and describedin U.S. Pat. No. 5,428,597.

The structure of a two-layer optical disk is shown in FIG. 11. As shownin FIG. 11, this two-layer optical disk comprises a first recordinglayer 1102 and a second recording layer 1104 disposed between a bottomresin base 1101 and a top resin base 1105 with a resin bonding layer1103 disposed between the two recording layers. Data bits 1126 arerecorded to the first and second recording layers in spiral orconcentric recording tracks. Note that the data bits 1126 may be formedas physical pits and lands, or as amorphous bits. Note also that thefirst recording layer 1102 is semi-transparent.

When reading this two-layer optical disk, light is emitted to the diskfrom only one side thereof, i.e., the side to which the resin base 1101is disposed in this example. The data recorded to the first recordinglayer 1102 can thus be read by focusing the emitted light on the firstrecording layer 1102. Because the first recording layer 1102 istransparent, data on the second recording layer 1104 can be read byfocusing the light on the second recording layer 1104 through the firstrecording layer 1102.

Applications for a two-layer optical disk include using both first andsecond recording layers to record movies and other types of extended,continuous information, and using the first recording layer to recordfirst information (such as a directory) and the second recording layerto record plural data referenced by the first information.

There has been proposed no system or method for sequentially recordingand reading the data on the two-layer optical disk.

SUMMARY OF THE INVENTION

Therefore, the object of the present invention is to provide a uniquemethod for recording and reading the data on the two-layer optical disk.

A further object of the present invention is to provide a two-layeroptical disk requiring a minimal amount of memory to achieve seamless(uninterrupted) data reproduction.

A further object of the invention is to provide a two-layer optical diskwhereby the seek time is minimized when referencing information.

A further object of the invention is to provide a two-layer optical diskwhereby tracking can be maintained irrespective of where the focus jump(refocusing) occurs.

To achieve the aforementioned objects, a two-layer optical diskcomprises: a first layer of a disk shaped recording medium for storingdata; a second layer of a disk shaped recording medium placed over saidfirst layer for storing data; a plurality of data blocks stored in saidfirst layer; and a plurality of data blocks stored in said second layer,said data blocks in said first and second layers being alternatelylinked to present one stream of information.

According to the two-layer optical disk of the present invention, thedata blocks in said first and second layers have different sizes.

According to the two-layer optical disk of the present invention, thedata blocks in said first and second layers have a same size.

According to the two-layer optical disk of the present invention, thedata blocks are sequentially aligned from the center of the layer to theperipheral of the layer, with the data blocks in the first layer takingodd numbered orders in the stream of information and the data blocks inthe second layer taking even numbered orders in the stream ofinformation.

According to the two-layer optical disk of the present invention, thedata blocks are sequentially aligned from the peripheral of the layer tothe center of the layer, with the data blocks in the first layer takingodd numbered orders in the stream of information and the data blocks inthe second layer taking even numbered orders in the stream ofinformation.

According to the two-layer optical disk of the present invention, thedata blocks in the first layer are aligned contiguously and said datablocks in the second layer are aligned contiguously.

According to the two-layer optical disk of the present invention, thedata blocks in the first layer are aligned contiguously and said datablocks in the second layer are aligned separately with a space betweenthe blocks.

The two-layer optical disk of the present invention, further comprisesdummy data filled in the second layer in areas other than the datablocks to make the total length of the data blocks in the second layerequal to that in the first layer.

The two-layer optical disk of the present invention, further comprisesfirst dummy data filled in the first layer in areas other than the datablocks and second dummy data filled in the second layer in areas otherthan the data blocks to make the total length of the data blocks in thefirst layer equal to that in the second layer.

According to another embodiment of the present invention, a two-layeroptical disk comprises: a first layer of a disk shaped recording mediumfor storing data; a second layer of a disk shaped recording mediumplaced over said first layer for storing data; a data block stored insaid first layer, said data block having an interruption position; atleast one auxiliary data block stored in said second layer, said datablock in said first layer being interrupted during a reproduction atsaid interruption position so as to enable a selection between (i)insert said auxiliary data block from the second layer, and (ii)continue without any insertion.

According to the present invention, a method for reproducing a two-layeroptical disk comprising: a first layer of a disk shaped recording mediumfor storing data; a second layer of a disk shaped recording mediumplaced over said first layer for storing data; a plurality of datablocks stored in said first layer; and a plurality of data blocks storedin said second layer, the method comprising the steps of:

(a) reading one block from said first layer;

(b) reading one block from said second layer;

(c) reading another block from said first layer; and

(d) reading another block from said second layer.

According to the method of the present invention, the one block andanother block in said first layer are adjacent to each other with saidone block located inner side of the first layer.

According to the method of the present invention, the one block andanother block in said second layer are adjacent to each other with saidone block located inner side of the second layer.

According to the method of the present invention, the one block andanother block in said first layer are adjacent to each other with saidone block located outer side of the first layer.

According to the method of the present invention, the one block andanother block in said second layer are adjacent to each other with saidone block located outer side of the second layer.

According to a further embodiment of the present invention, a method forreproducing a two-layer optical disk comprising: a first layer of a diskshaped recording medium for storing data; a second layer of a diskshaped recording medium placed over said first layer for storing data; adata block stored in said first layer, said data block having aninterruption position; and at least one auxiliary data block stored insaid second layer, said method comprising the steps of:

(a) reading said data block in said first layer up to said interruptionposition;

(b) selecting between (i) insert said auxiliary data block from thesecond layer at said interruption position, and (ii) continue withoutany insertion;

(c) when said (i) is selected, insert said auxiliary data block from thesecond layer at said interruption position, and thereafter continuereading the data block in said first layer from said interruptionposition; and

(d) when said (ii) is selected, continue reading the data block withoutany insertion.

With a two-layer optical disk thus comprised, the data seek distance fordata recorded across the first and second recording layers will alwaysbe less than the total radius of the recording area. The seek time istherefore less than with conventional two-layer optical disks, and thememory required for seamless (uninterrupted) reproduction can thereforealso be reduced.

With a two-layer optical disk thus comprised, the data seek distance fordata recorded across the first and second recording layers will alwaysbe less than the total radius of the recording area and less than aconstant value. The seek time is therefore less than with conventionaltwo-layer optical disks and less than a constant value, and the memoryrequired for seamless (uninterrupted) reproduction can also be aconstant amount less than conventionally required.

The seek time when accessing information called from the firstinformation is also less than conventionally, and the wait time whenreferencing this second information can therefore also be shortenedbecause the seek time is shortened by this configuration.

Tracking can also be maintained after refocusing irrespective of whererefocusing occurs, and system errors can therefore be prevented, becausea signal track is always recorded at substantially the same radialpositions on both recording layers with the configuration of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given below and the accompanying diagrams wherein:

FIG. 1A is a cross sectional diagram of a two-layer optical diskaccording to the first embodiment of the invention, and FIG. 1B is usedto describe the arrangement of the data recorded thereby.

FIG. 2A is a cross sectional diagram of a two-layer optical diskaccording to the second embodiment of the invention, and FIG. 2B is usedto describe the arrangement of the data recorded thereby.

FIG. 3A is a cross sectional diagram of a two-layer optical diskaccording to the third embodiment of the invention, and FIG. 3B is usedto describe the arrangement of the data recorded thereby.

FIG. 4A is a cross sectional diagram of a two-layer optical diskaccording to the fourth embodiment of the invention, and FIG. 4B is usedto describe the arrangement of the data recorded thereby.

FIG. 5A is a cross sectional diagram of a two-layer optical diskaccording to the fifth embodiment of the invention, and FIG. 5B is usedto describe the arrangement of the data recorded thereby.

FIG. 6A is a cross sectional diagram of a two-layer optical diskaccording to the sixth embodiment of the invention, and FIG. 6B is usedto describe the arrangement of the data recorded thereby.

FIG. 7A is a cross sectional diagram of a two-layer optical diskaccording to the seventh embodiment of the invention, and FIG. 7B isused to describe the arrangement of the data recorded thereby.

FIG. 8A is a cross sectional diagram of a two-layer optical diskaccording to the eighth embodiment of the invention, and FIG. 8B is usedto describe the arrangement of the data recorded thereby.

FIG. 9A is a cross sectional diagram of a two-layer optical diskaccording to the ninth embodiment of the invention, and FIG. 9B is usedto describe the arrangement of the data recorded thereby.

FIG. 10A is a cross sectional diagram of a two-layer optical diskaccording to the tenth embodiment of the invention, and FIG. 10B is usedto describe the arrangement of the data recorded thereby.

FIG. 11 is a cross sectional diagram of a conventional two-layer opticaldisk.

DESCRIPTION OF PREFERRED EMBODIMENTS

The preferred embodiments of the present invention are described belowwith reference to the accompanying figures.

Embodiment 1

FIG. 1A is a cross sectional diagram of a two-layer optical diskaccording to a preferred embodiment of the invention. Shown in FIG. 1Aare the resin base 1, first recording layer 2, resin bond layer 3,second recording layer 4, and resin base 5. Data bits 16 are recorded tothe first and second recording layers in spiral or concentric recordingtracks. Note that the data bits 16 may be formed as physical pits andlands, or as amorphous bits formed by effecting a (chemical) phasechange in the recording film. The first and second recording layers 2and 4 are made of thin metallic films. For example, the first recordinglayer 2 is made of an aluminum layer of 80 nm, and the second recordinglayer 2 is made of a gold layer of 13 nm. For the first and secondlayers, other metals, such as a compound of Ge.Te.Sb can be used. Thesame applies for the other embodiments.

The arrangement of data recorded to a two-layer optical disk accordingto this first embodiment is shown in FIG. 1B. As shown in FIG. 1B, thefirst data block 7 obtained by dividing the continuous information intoplural blocks is recorded to the first recording layer from position 6(radius r6) toward the outside circumference of the disk to position 8(radius r8), and the third data block 9 is next recorded from position 8(radius r8) to position 10 (radius r10). The second data block 12,similarly obtained by dividing the continuous source data, is recordedto the second recording layer toward the outside circumference fromposition 11 (radius r11) to position 13 (radius r13), and the fourthdata block 14 is then recorded to position 15 (radius r15).

It should be noted that the capacity of each data block is less than theentire storage capacity of the first recording layer.

Operation with a two-layer optical disk thus comprised is describedbelow.

Different size blocks 7, 12, 9 and 14 are read sequentially in saidorder. Note that the first recording layer 2 contains the odd numberedorders (first and third) of the reading sequence blocks, and the secondrecording layer 4 contains the even numbered orders (second and fourth)of the reading sequence blocks. For this purpose, a table indicating theaddresses at positions 6, 8, 11, 13, 8, 10, 13, 15 is recorded in acontrol data area in the optical disk. By following the positions 6, 8,11, 13, 8, 10, 13, 15 sequentially, the above sequential reading can beaccomplished. The recording can be done in a similar manner.

When the recorded information is reproduced continuously, it isnecessary to seek position 11 from position 8 after reproducing thefirst data block 7. This seek time T11 can be written T11=Tj+Ts(d11)where Tj is the refocusing time from position 8 to 8', and Ts(d11) isthe seek time for distance d11 from radius r8 to radius r11(d11=r8-r11).

Position 8 is a position within the recording area between the recordingstart and end positions in the present embodiment. As a result,d11<d101, and the seek time Ts(d11) is therefore less than Ts(d101). Theseek time is T11<T101, so the seek (access) time is reduced, and lessmemory is required for seamless (uninterrupted) reproduction.

After the second data block 12 is reproduced, it is again necessary toseek position 8 from position 13. This seek time T12 can be writtenT12=Tj+Ts(d12) where Tj is the refocusing time from position 13 to 13',and Ts(d12) is the seek time for distance d12 from radius r13' to radiusr8 (d12=r8-r13).

Positions 8 and 13 are positions within the recording area between therecording start and end positions in the present embodiment. As aresult, d12<d101, and the seek time Ts(d12) is therefore less thanTs(d101). The seek time is T12<T101, so the seek (access) time isreduced, and less memory is required for seamless (uninterrupted)reproduction.

After the third data block 9 is reproduced, it is again necessary toseek position 13 from position 10. This seek time T13 can be writtenT13=Tj+Ts(d13) where Tj is the refocusing time from position 13' to 13,and Ts(d13) is the seek time for distance d13 from radius r10 to radiusr13' (d13=r10-r13).

Position 13 is within the recording area between the recording start andend positions in the present embodiment. As a result, d13<d101, and theseek time Ts(d13) is therefore less than Ts(d101). The seek time isT13<T101, so the seek (access) time is reduced, and less memory isrequired for seamless (uninterrupted) reproduction.

It should be noted that the first embodiment above has been describedwith reference to two-layer optical disks sequentially recorded startingwith the first data block at the inside circumference and recordingtoward the outside circumference. The invention shall not be thuslimited, however, and the same effect can be obtained recording from theoutside circumference toward the inside circumference. It will also beobvious that positions 6 and 11 may be the recording start position atthe outside circumference of the disk.

With a two-layer optical disk comprising two data recording layerswhereby the data recorded to both layers can be detected by emittinglight to the recording layers from only one side of the diskcharacterized according to the present embodiment by dividing thecontinuous information into three or more plural data blocks where thecapacity of each data block is less than the storage capacity of onerecording layer, and then recording the odd-numbered data blocks to onerecording layer either from the inside circumference to the outsidecircumference, or from the outside circumference to the insidecircumference, and recording the even-numbered data blocks to the otherrecording layer from the inside circumference to the outsidecircumference, or from the outside circumference to the insidecircumference, the seek distance in the data block recording area isless than the radius of the total recording area. The seek time cantherefore be shortened, and the memory requirement for seamless(uninterrupted) reproduction can be reduced.

Embodiment 2

FIG. 2A is a cross sectional diagram of a two-layer optical diskaccording to an alternative embodiment of the invention. Shown in FIG.2A are the resin base 17, first recording layer 18, resin bond layer 19,second recording layer 20, and resin base 21. Data bits 22 are recordedto the first and second recording layers in spiral or concentricrecording tracks. Note that the data bits 16 may be formed as physicalpits and lands, or as amorphous bits formed by effecting a (chemical)phase change in the recording film.

The arrangement of data recorded to a two-layer optical disk accordingto this first embodiment is shown in FIG. 2B. As shown in FIG. 2B, thefirst data block 23 obtained by dividing the continuous information intoplural blocks is recorded to the first recording layer from position 22(radius r22) at the inside circumference toward the outsidecircumference of the disk to position 24 (radius r24), the third datablock 25 is next recorded to position 26 (radius r26), the fifth datablock 27 is then recorded to position 28 (radius r28), and the seventhdata block 29 is recorded to position 30 (radius r30).

Data is similarly recorded to the second recording layer. The seconddata block 32 obtained by dividing the continuous information intoplural blocks is recorded from position 31 (radius r31) at the insidecircumference toward the outside circumference of the disk to position33 (radius r33), the fourth data block 34 is next recorded to position35 (radius r35), and the sixth data block 36 is recorded to position 37(radius r37).

It should be noted that the capacity of each data block is less than theentire storage capacity of one recording layer, and each data block isequal in size. The recording start position 31 of the second data blockis also controlled so that r22≦r31≦r24.

Furthermore, if the diameter of the first data block on the recordinglayer is d23, the diameter of the second data block is d32, the diameterof the third data block is d25, the diameter of the fourth data block isd34, the diameter of the fifth data block is d27, the diameter of thesixth data block is d36, and the diameter of the seventh data block isd29, d23=d32=d25=d34=d29=d36 when data is recorded so that the datavolume per revolution is equal. When the data is recorded with aconstant bit length, d23≧d32≧d25≧d34≧d29≧d36.

Operation with a two-layer optical disk thus comprised is describedbelow.

The same size blocks 23, 32, 25, 34, 27, 36 and 29 are read sequentiallyin said order. Note that the first recording layer 18 contains the oddnumbered orders (first, third, fifth and seventh) of the readingsequence blocks, and the second recording layer 20 contains the evennumbered orders (second, fourth and sixth) of the reading sequenceblocks. For this purpose, a counter for counting one block size may beprovided in a reproducing circuit. Instead of the counter, a table asdescribed in the first embodiment can be stored in the optical disk. Therecording can be done in a similar manner.

When the recorded information is reproduced continuously, it isnecessary to seek position 31 from position 24 after reproducing thefirst data block 23. This seek time T21 can be written T21=Tj+Ts(d21)where Tj is the refocusing time from position 24 to 24', and Ts(d21) isthe seek time for distance d21 from radius r24' to radius r31(d21=r24-r31).

Distance d21 is always less than d101 with the present embodimentbecause the data block capacity is less than the total capacity of therecording layer. As a result, the seek time Ts(d21) from 24' to 31 isshort. In addition, 0≦d21≦r33-r31=d32≦d23 because r22≦r31≦r24, andTs(d21)≦Ts(d23) if Ts(d23) is the seek time for distance d23. Distanced23 is determined by the capacity of the first data block, but isconstant in the present embodiment because each data block is equal insize. Seek time Ts(d23) is therefore also constant. Thus,T21=Tj+Ts(d21), and T21≦Tj+Ts(d23), the required memory is a constantsize equivalent to that sufficient to store the data output during timeTj+Ts(d23), and the drive design is thus simplified.

It will also be obvious that in this second embodiment position 22 maybe the recording start position at the outside circumference of thedisk.

With a two-layer optical disk comprising two data recording layerswhereby the data recorded to both layers can be detected by emittinglight to the recording layers from only one side of the disk accordingto the present embodiment, continuous information is divided into pluraldata blocks where the capacity of each data block is less than thestorage capacity of one recording layer and is equal in each data block,the odd-numbered data blocks are then recorded to one recording layereither from the inside circumference to the outside circumference andthe even-numbered data blocks are then recorded to the other recordinglayer from the inside circumference to the outside circumference withthe second data block recorded from a radial position within therecording area of the first data block. The seek time can therefore beshortened, and the memory required for seamless (uninterrupted)reproduction can be reduced to less than a known constant amount.

Embodiment 3

FIG. 3A is a cross sectional diagram of a two-layer optical diskaccording to a third embodiment of the invention. Shown in FIG. 3A arethe resin base 38, first recording layer 39, resin bond layer 40, secondrecording layer 41, and resin base 42. Data bits 43 are recorded to thefirst and second recording layers in spiral or concentric recordingtracks. Note that the data bits 43 may be formed as physical pits andlands, or as amorphous bits formed by effecting a (chemical) phasechange in the recording film.

The arrangement of data recorded to a two-layer optical disk accordingto this third embodiment is shown in FIG. 3B. As shown in FIG. 3B, thefirst information 45 is recorded across the first recording layer fromposition 44 (radius r44) at the inside circumference to position 46(radius r46) at approximately the outside circumference of the disk.

The second data block 48 called from the first information 45 isrecorded to the second recording layer from position 47 (radius r47) toposition 49 (radius r49) such that r47≦r56≦r49. Note that position 56(radius r56) here is the position in the first information at which thecall to the second information is generated.

The third data block 51 called from the first information 45 is recordedto the second recording layer from position 50 (radius r50) to position52 (radius r52) such that r50≦r57≦r52. Note that position 57 (radiusr57) here is the position in the first information at which the call tothe third data block 51 is generated.

The fourth data block 54 called from the first information 45 isrecorded to the second recording layer from position 53 (radius r53) toposition 55 (radius r55) such that r53≦r58≦r55. Note that position 58(radius r58) here is the position in the first information at which thecall to the fourth data block 54 is generated.

Operation with a two-layer optical disk thus comprised is describedbelow.

A block 45 is read from the beginning 44 to the end 46, but the readingis temporarily stopped at interruption positions 56, 57 and 58. Atinterruption position 56, a selection between (i) insert an auxiliarydata block 48, and (ii) continue without any insertion, is made.Similarly, at interruption position 57, a selection between (i) insertan auxiliary data block 51, and (ii) continue without any insertion, ismade, and at interruption position 58, a selection between (i) insert anauxiliary data block 54, and (ii) continue without any insertion, ismade. The block 45 may be a game software, and auxiliary blocks 48, 51and 54 may be interruptions providing explanations on how to proceed thegame.

When the information thus recorded is reproduced, a call to access thesecond data block 48 is generated at position 56 while reproducing thefirst information. This makes it necessary to seek position 47 fromposition 56. This seek time T31 can be written T31=Tj+Ts(d31) where Tjis the refocusing time from position 56 to 56', and Ts(d31) is the seektime for distance d31 from radius r56' to radius r47 (d31=r56-r47).Because r47≦r56≦r49, 0≦d31≦r49-r47.

The seek time is therefore reduced, and the wait time is thereforereduced, because the seek distance is always shorter than the distance(r49-r47) corresponding to the size of the data blocks used to recordthis second information. This is also true when seeking position 50 fromposition 57 to access the third data block 51, and when seeking position53 from position 58 to access the fourth data block 54.

With a two-layer optical disk comprising two data recording layerswhereby the data recorded to both layers can be detected by emittinglight to the recording layers from only one side of the disk accordingto the present embodiment, data of a first information type is recordedto one recording layer, plural data that can be called from the firstinformation is recorded to the other recording layer, and theinformation that can be called from the first information is recorded ina form covering a radial position in the first information from whichthe call may be generated. The seek time required to access informationon the second recording layer from the first information recorded to thefirst recording layer can therefore be reduced, and the wait time canthus be reduced.

It should be noted that the present embodiment has been described withreference to two-layer optical disks on which data is recorded from theinside circumference toward the outside circumference. The inventionshall not be thus limited, however, and the same effect can be obtainedrecording from the outside circumference toward the insidecircumference.

Embodiment 4

FIG. 4A is a cross sectional diagram of a two-layer optical diskaccording to a fourth embodiment of the invention. Shown in FIG. 4A arethe resin base 59, first recording layer 60, resin bond layer 61, secondrecording layer 62, and resin base 63. Data bits 64 are recorded to thefirst and second recording layers in spiral or concentric recordingtracks. Note that the data bits 64 may be formed as physical pits andlands, or as amorphous bits formed by effecting a (chemical) phasechange in the recording film.

The arrangement of data recorded to a two-layer optical disk accordingto this embodiment is shown in FIG. 4B. Note that like reference numbersare used for like parts in FIGS. 4B and 1B.

Referring to FIG. 4B, dummy data 66, 67, 70, and 71 are respectivelyrecorded in the area from the recording start position 65 (radius r65)of the recording area in the first recording layer to the recordingstart position 6 (radius r6) of the first data block 7; the area fromthe end point 10 (radius r10) of the third data block 9 to the end point68 (radius r68) of the first recording layer; the area from therecording start position 69 (radius r69) of the recording area in thesecond recording layer to the recording start position 11 (radius r11)of the second data block 12; and the area from the end point 15 (radiusr15) of the fourth data block 14 to the end point 72 (radius r72) of thesecond recording layer.

Operation with a two-layer optical disk thus comprised is describedbelow.

The operation is the same as the first embodiment.

Recording dummy data as thus described assures that data is recorded tothe entire recording area of both the first and second recording layers.This assures that data is recorded wherever the read beam is refocusedon the first and second recording layers, enabling tracking to bemaintained and thus preventing system errors.

With a two-layer optical disk comprising two data recording layerswhereby the data recorded to both layers can be detected by emittinglight to the recording layers from only one side of the disk accordingto the present embodiment, tracking can be maintained, and system errorsthereby prevented, irrespective of where the focus is readjusted byrecording dummy data to those parts of the recording areas to whichmeaningful data is not recorded on the first and second recordinglayers.

It will be obvious that while this embodiment has been described asrecording dummy data to the blank data areas, any type of informationmay be recorded insofar as the recorded data forms bit sequence signaltracks.

It should be noted that this fourth embodiment has been described assequentially recording all data blocks from the inside circumferencetoward the outside circumference. The invention shall not be so limited,however, and the same effect can be obtained by recording from theoutside circumference toward the inside circumference.

Embodiment 5

FIG. 5A is a cross sectional diagram of a two-layer optical diskaccording to a fifth embodiment of the invention. Shown in FIG. 5A arethe resin base 73, first recording layer 74, resin bond layer 75, secondrecording layer 76, and resin base 77. Data bits 78 are recorded to thefirst and second recording layers in spiral or concentric recordingtracks. Note that the data bits 78 may be formed as physical pits andlands, or as amorphous bits formed by effecting a (chemical) phasechange in the recording film.

The arrangement of data recorded to a two-layer optical disk accordingto this embodiment is shown in FIG. 5B. Note that like reference numbersare used for like parts in FIGS. 5B and 1B. Note also that dummy data 79is recorded to the second recording layer from position 15 (radius r15)to position 80 (radius r10).

Operation with a two-layer optical disk thus comprised is describedbelow.

The operation is the same as the first embodiment.

Recording dummy data 79 as thus described assures that data is recordedto the second recording layer at any radial position at which data isrecorded to the first recording layer. This assures that data isrecorded wherever the read beam is refocused during data reproduction,and tracking can therefore be maintained to prevent system errors. Diskproduction time can also be reduced because the amount of dummy datarecorded is minimized.

With a two-layer optical disk comprising two data recording layerswhereby the data recorded to both layers can be detected by emittinglight to the recording layers from only one side of the disk accordingto the present embodiment, tracking can be maintained irrespective ofwhere the focus is readjusted by recording dummy data to the recordinglayer to which meaningful data is not recorded at any radial positionwhereat meaningful information is recorded to one recording layer but isnot recorded to the other recording layer.

It will be obvious that while this embodiment has been described asrecording dummy data to the blank data areas described above, any typeof information may be recorded insofar as the recorded data forms bitsequence signal tracks.

It should be noted that this embodiment has been described assequentially recording all data blocks from the inside circumferencetoward the outside circumference. The invention shall not be so limited,however, and the same effect can be obtained by recording from theoutside circumference toward the inside circumference.

Embodiment 6

FIG. 6A is a cross sectional diagram of a two-layer optical diskaccording to a sixth embodiment of the invention. Shown in FIG. 6A arethe resin base 81, first recording layer 82, resin bond layer 83, secondrecording layer 84, and resin base 85. Data bits 86 are recorded to thefirst and second recording layers in spiral or concentric recordingtracks. Note that the data bits 86 may be formed as physical pits andlands, or as amorphous bits formed by effecting a (chemical) phasechange in the recording film.

Referring to FIG. 6B, dummy data 88, 89, 92, and 93 are respectivelyrecorded in the area from the recording start position 87 (radius r87)of the recording area in the first recording layer to the recordingstart position 22 (radius r22) of the first data block 23; the area fromthe end point 30 (radius r30) of the seventh data block 29 to the endpoint 90 (radius r90) of the first recording layer; the area from therecording start position 91 (radius r91) of the recording area in thesecond recording layer to the recording start position 31 (radius r31)of the second data block 32; and the area from the end point 37 (radiusr37) of the sixth data block 36 to the end point 94 (radius r94) of thesecond recording layer.

Operation with a two-layer optical disk thus comprised is describedbelow.

The operation is the same as the second embodiment.

Recording dummy data as thus described assures that data is recorded tothe entire recording area of both the first and second recording layers.This assures that data is recorded wherever the read beam is refocusedon the first and second recording layers, enabling tracking to bemaintained and thus preventing system errors.

With a two-layer optical disk comprising two data recording layerswhereby the data recorded to both layers can be detected by emittinglight to the recording layers from only one side of the disk accordingto the present embodiment, tracking can be maintained, and system errorsthereby prevented, irrespective of where the focus is readjusted byrecording dummy data to those parts of the recording areas to whichmeaningful data is not recorded on the first and second recordinglayers.

It will be obvious that while this embodiment has been described asrecording dummy data to the blank data areas, any type of informationmay be recorded insofar as the recorded data forms bit sequence signaltracks.

It should be noted that this sixth embodiment has been described assequentially recording all data blocks from the inside circumferencetoward the outside circumference. The invention shall not be so limited,however, and the same effect can be obtained by recording from theoutside circumference toward the inside circumference.

Embodiment 7

FIG. 7A is a cross sectional diagram of a two-layer optical diskaccording to a fifth embodiment of the invention. Shown in FIG. 7A arethe resin base 95, first recording layer 96, resin bond layer 97, secondrecording layer 98, and resin base 99. Data bits 100 are recorded to thefirst and second recording layers in spiral or concentric recordingtracks. Note that the data bits 100 may be formed as physical pits andlands, or as amorphous bits formed by effecting a (chemical) phasechange in the recording film.

The arrangement of data recorded to a two-layer optical disk accordingto this embodiment is shown in FIG. 7B. Note that like reference numbersare used for like parts in FIGS. 7B and 1B. Note also that dummy data102 and 103 are respectively recorded to the second recording layer fromposition 101 (radius r22) to the starting point 31 (radius r31) of thesecond data block 32, and from the end point 37 (radius r37) of thesixth data block 36 to position 104 at radius r30 on the secondrecording layer.

Operation with a two-layer optical disk thus comprised is describedbelow.

The operation is the same as the second embodiment.

Recording dummy data 102 and 103 as thus described assures that data isrecorded to the second recording layer at the same radial positions ofthe first recording layer to which data is recorded. This assures thatdata is recorded wherever the read beam is refocused during datareproduction, and tracking can therefore be maintained to prevent systemerrors. Disk production time can also be reduced because the amount ofdummy data recorded is minimized.

With a two-layer optical disk comprising two data recording layerswhereby the data recorded to both layers can is be detected by emittinglight to the recording layers from only one side of the disk accordingto the present embodiment, tracking can be maintained irrespective ofwhere the focus is readjusted, and disk production time can be reducedbecause less dummy data is recorded, by recording dummy data to therecording layer to which meaningful data is not recorded at any radialposition whereat meaningful information is recorded to one recordinglayer but is not recorded to the other recording layer.

It will be obvious that while this embodiment has been described asrecording dummy data to the blank data areas described above, any typeof information may be recorded insofar as the recorded data forms bitsequence signal tracks.

It should be noted that this embodiment has been described assequentially recording all data blocks from the inside circumferencetoward the outside circumference. The invention shall not be so limited,however, and the same effect can be obtained by recording from theoutside circumference toward the inside circumference.

Embodiment 8

FIG. 8A is a cross sectional diagram of a two-layer optical diskaccording to an eighth embodiment of the invention. Shown in FIG. 8A arethe resin base 105, first recording layer 106, resin bond layer 107,second recording layer 108, and resin base 109. Data bits 110 arerecorded to the first and second recording layers in spiral orconcentric recording tracks. Note that the data bits 110 may be formedas physical pits and lands, or as amorphous bits formed by effecting a(chemical) phase change in the recording film.

Referring to FIG. 8B, dummy data 112, 113, 116, 117, 118, and 119 arerespectively recorded in the area from the recording start position 111(radius r111) at the inside circumference of the recording area in thefirst recording layer to the recording start position 44 (radius r44) ofthe first information 45; the area from the end point 46 (radius r46) ofthe first information 45 to the end point 114 (radius r114) of therecording area; from the recording start position 115 (radius r115) atthe inside circumference of the recording area in the second recordinglayer to the starting point 47 (radius r47) of the second data block 48;from the end point 49 of the second data block 48 (radius r49) to thestarting point 50 (radius r50) of the third data block 51; from the endpoint 52 of the third data block 51 (radius r52) to the starting point53 (radius r53) of the fourth data block 54; and from the end point 55(radius r55) of the fourth data block 54 to the end point 120 of therecording area (radius r120).

Operation with a two-layer optical disk thus comprised is describedbelow.

The operation is the same as the third embodiment.

Recording dummy data as thus described assures that data is recorded tothe entire recording area of both the first and second recording layers.This assures that data is recorded wherever the read beam is refocusedon the first and second recording layers, enabling tracking to bemaintained and thus preventing system errors.

With a two-layer optical disk comprising two data recording layerswhereby the data recorded to both layers can be detected by emittinglight to the recording layers from only one side of the disk accordingto the present embodiment, tracking can be maintained, and system errorsthereby prevented, irrespective of where the focus is readjusted byrecording dummy data to those parts of the recording areas to whichmeaningful data is not recorded on the first and second recordinglayers.

It will be obvious that while this embodiment has been described asrecording dummy data to the blank data areas, any type of informationmay be recorded insofar as the recorded data forms bit sequence signaltracks.

It should be noted that this eighth embodiment has been described assequentially recording all data blocks from the inside circumferencetoward the outside circumference. The invention shall not be so limited,however, and the same effect can be obtained by recording from theoutside circumference toward the inside circumference.

Embodiment 9

FIG. 9A is a cross sectional diagram of a two-layer optical diskaccording to a ninth embodiment of the invention. Shown in FIG. 9A arethe resin base 121, first recording layer 122, resin bond layer 123,second recording layer 124, and resin base 125. Data bits 126 arerecorded to the first and second recording layers in spiral orconcentric recording tracks. Note that the data bits 126 may be formedas physical pits and lands, or as amorphous bits formed by effecting a(chemical) phase change in the recording film.

The arrangement of data recorded to a two-layer optical disk accordingto this embodiment is shown in FIG. 9B. Note that like reference numbersare used for like parts in FIGS. 9B and 3B.

Referring to FIG. 9B, dummy data 128, 129, 130, and 131 are respectivelyrecorded in the area from the recording start position 127 (radius r44)of the recording area in the second recording layer to the recordingstart position 47 (radius r47) of the second data block 48 (secondinformation); the area from the end point 49 (radius r49) of the seconddata block 48 to the starting point 50 (radius r50) of the third datablock 51; from the end point 52 (radius r52) of the of the third datablock 51 to the recording start position 53 (radius r53) of the fourthdata block 54; and from the end point 55 (radius r55) of the fourth datablock 54 to position 132 at radius r46 of the second recording layer.

Operation with a two-layer optical disk thus comprised is describedbelow.

The operation is the same as the third embodiment.

Recording dummy data 128, 129, 130, and 131 as thus described assuresthat data is recorded to the second recording layer at any radialposition at which data is recorded to the first recording layer. Thisassures that data is recorded wherever the read beam is refocused duringdata reproduction, and tracking can therefore be maintained to preventsystem errors. Disk production time can also be reduced because theamount of dummy data recorded is minimized.

With a two-layer optical disk comprising two data recording layerswhereby the data recorded to both layers can be detected by emittinglight to the recording layers from only one side of the disk accordingto the present embodiment, tracking can be maintained irrespective ofwhere the focus is readjusted by recording dummy data to the recordinglayer to which meaningful data is not recorded at any radial positionwhereat meaningful information is recorded to one recording layer but isnot recorded to the other recording layer.

It will be obvious that while this embodiment has been described asrecording dummy data to the blank data areas described above, any typeof information may be recorded insofar as the recorded data forms bitsequence signal tracks.

It should be noted that this embodiment has been described assequentially recording all data blocks from the inside circumferencetoward the outside circumference. The invention shall not be so limited,however, and the same effect can be obtained by recording from theoutside circumference toward the inside circumference.

Embodiment 10

FIG. 10A is a cross sectional diagram of a two-layer optical diskaccording to a sixth embodiment of the invention. Shown in FIG. 10A arethe resin base 1017, first recording layer 1018, resin bond layer 1019,second recording layer 1020, and resin base 1021. Data bits 1022 arerecorded to the first and second recording layers in spiral orconcentric recording tracks. Note that the data bits 1022 may be formedas physical pits and lands, or as amorphous bits formed by effecting a(chemical) phase change in the recording film.

The arrangement of data recorded to a two-layer optical disk accordingto this embodiment is shown in FIG. 10B. As shown in FIG. 10B, the firstdata block 1023 obtained by dividing the continuous information intoplural blocks is recorded to the first recording layer from position1022 (radius r1022) at the outside circumference of the disk to position1024 (radius r1024) toward the inside circumference, the third datablock 1025 is next recorded to position 1026 (radius r1026), the fifthdata block 1027 is next recorded to position 1028 (radius r1028), andthe seventh data block 1029 is next recorded to position 1030 (radiusr1030).

The second data block 1032, similarly obtained by dividing thecontinuous source data, is likewise recorded from position 1031 (radiusr1031) near the outside circumference to position 1033 (radius r1033)toward the inside circumference, the fourth data block 1034 is thenrecorded to position 1035 (radius r1035), and the sixth data block 1036is recorded to position 1037 (radius r1037).

It should be noted that the capacity of each data block is less than theentire storage capacity of one recording layer, and is the same for eachdata block. The starting point 1031 of the second data block is alsocontrolled such that r1022≧r1031≧r1024.

Furthermore, if the diameter of the first data block on the recordinglayer is d1023, the diameter of the second data block is d1032, thediameter of the third data block is d1025, the diameter of the fourthdata block is d1034, the diameter of the fifth data block is d1027, thediameter of the sixth data block is d1036, and the diameter of theseventh data block is d1029, d1023=d1032=d1025=d1034=d1029=d1036 whendata is recorded so that the data volume per revolution is equal. Whenthe data is recorded with a constant bit length,d1023≦d1032≦d1025≦d1034≦d1029≦d1036.

Operation with a two-layer optical disk thus comprised is describedbelow.

The operation is the same as the first embodiment, but the data is readnot from the inside to the outside, but from outside to the inside ofthe optical disk.

When the recorded information is reproduced continuously, it isnecessary to seek position 1031 from position 1024 after reproducing thefirst data block 1023. This seek time T1021 can be writtenT1021=Tj+Ts(d1021) where Tj is the refocusing time from position 1024 to1024', and Ts(d1021) is the seek time for distance d1021 from radiusr1024' to radius r1031 (d1021=r1031-r1024).

Distance d1021 is always less than d101 with the present embodimentbecause the data block capacity is less than the total capacity of therecording layer. As a result, the seek time Ts(d1021) from 1024' to 1031is short. In addition, 0≦d1021≦r1031-r1033=d1032≦d1036 becauser1022≦r1031≦r1024, and Ts(d1021)≦Ts(d1036) if Ts(d1036) is the seek timefor distance d1036. Distance d1036 is determined by the capacity of theseventh data block, but is constant in the present embodiment becauseeach data block is equal in size. Seek time Ts(d1036) is therefore alsoconstant. Thus, T1021=Tj+Ts(d1021), and T1021≦Tj+Ts(d1036), the requiredmemory is a constant size equivalent to that sufficient to store thedata output during time Tj+Ts(d1036), and the drive design is thussimplified.

With a two-layer optical disk comprising two data recording layerswhereby the data recorded to both layers can be detected by emittinglight to the recording layers from only one side of the disk accordingto the present embodiment, continuous information is divided into pluraldata blocks where the capacity of each data block is less than thestorage capacity of one recording layer and is equal in each data block,the odd-numbered data blocks are then recorded to one recording layerfrom the outside circumference to the inside circumference, and theeven-numbered data blocks are recorded to the other recording layer fromthe outside circumference to the inside circumference with the seconddata block starting from a radial position at which the first data blockis present. The seek time can therefore be shortened, and the memoryrequired for seamless (uninterrupted) reproduction can be reduced toless than a known constant amount.

Effects of the invention

An two-layer optical disk comprising two data recording layers wherebythe data recorded to both layers can be detected by emitting light tothe recording layers from only one side of the disk according to thepresent invention records data blocks obtained by dividing continuousinformation into three or more plural data blocks where the capacity ofeach data block is less than the storage capacity of one recordinglayer. More specifically, the odd-numbered data blocks are recorded toone recording layer either from the inside circumference to the outsidecircumference, or from the outside circumference to the insidecircumference, and the even-numbered data blocks are recorded to theother recording layer from the inside circumference to the outsidecircumference, or from the outside circumference to the insidecircumference. The data seek distance for data recorded across the firstand second recording layers is therefore reduced and, the search timecan thus be shortened. The memory required for seamless (uninterrupted)reproduction can also be reduced, and an outstanding two-layer opticaldisk can be achieved.

A two-layer optical disk comprising two data recording layers wherebythe data recorded to both layers can be detected by emitting light tothe recording layers from only one side of the disk according to thepresent invention records data blocks obtained by dividing continuousinformation into plural data blocks where the capacity of each datablock is less than the storage capacity of one recording layer, and thecapacity of each data block is the same. More specifically, theodd-numbered data blocks are recorded to one recording layer either fromthe inside circumference to the outside circumference, or from theoutside circumference to the inside circumference, and the even-numbereddata blocks are recorded to the other recording layer from the insidecircumference to the outside circumference, or from the outsidecircumference to the inside circumference, with the second data blockrecorded starting from a radial position at which the first data blockis present. The data seek distance for data recorded across the firstand second recording layers is therefore reduced, and is less than aknown distance, the search time can thus be shortened, the memoryrequired for seamless (uninterrupted) reproduction can be reduced, andan outstanding two-layer optical disk can be achieved.

A two-layer optical disk comprising two data recording layers wherebythe data recorded to both layers can be detected by emitting light tothe recording layers from only one side of the disk records, accordingto the present invention, a first type of information to one recordinglayer, and records plural data that can be called by the firstinformation to the other recording layer in a format including a radialposition in the first information from which the call may be generated.An outstanding two-layer optical disk whereby the seek distance requiredto access data called from the first information is reduced, and thesearch time can therefore be reduced, and the wait time is thusshortened, can therefore be achieved.

A two-layer optical disk comprising two data recording layers wherebythe data recorded to both layers can be detected by emitting light tothe recording layers from only one side of the disk comprises accordingto the present invention recording tracks on both recording layers tosubstantially the same radial position. An outstanding two-layer opticaldisk whereby tracking can be maintained after refocusing irrespective ofwhere refocusing occurs can therefore be achieved.

The embodiments 1 to 10 described above can be classified as shown inthe table below.

                  TABLE    ______________________________________               Without  With dummy               dummy    Up to edge Partial    ______________________________________    Odd/Even     Embo. 1    Embo. 4    Embo. 5    Various block    size    Odd/Even     Embo. 2    Embo. 6    Embo. 7    Same block size                 (Embo. 10)    With interrup-                 Embo. 3    Embo. 8    Embo. 9    tion    ______________________________________

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

What is claimed is:
 1. A two-layer optical disk, comprising:a firstlayer of a disk-shaped recording medium for storing data; a second layerof a disk-shaped recording medium, positioned over said first layer, forstoring data; a plurality of data blocks stored in said first layer; anda plurality of data blocks stored in said second layer, said data blocksin said first layer and said data blocks in said second layer beingalternately linked to present one stream of information, wherein saidplurality of data blocks in said first layer and said plurality of datablocks in second layer have a same size.
 2. A two-layer optical disk,comprising:a first layer of a disk-shaped recording medium for storingdata; a second layer of a disk-shaped recording medium, positioned oversaid first layer, for storing data; a plurality of data blocks stored insaid first layer; a plurality of data blocks stored in said secondlayer, said data blocks in said first layer and said data blocks in saidsecond layer being alternately linked to present one stream ofinformation; and dummy data filled in said second layer in areasdifferent from said plurality of data blocks to make a total length ofsaid plurality of data blocks in said second layer equal to a totallength of said plurality of data blocks in said first layer.
 3. Atwo-layer optical disk, comprising:a first layer of a disk-shapedrecording medium for storing data; a second layer of a disk-shapedrecording medium, positioned over said first layer, for storing data; aplurality of data blocks stored in said first layer; a plurality of datablocks stored in said second layer, said data blocks in said first layerand said data blocks in said second layer being alternately linked topresent one stream of information; first dummy data filled in said firstlayer in areas different from said plurality of data blocks; and seconddummy data filled in said second layer in areas different from saidplurality of data blocks to make a length of said plurality of datablocks in said first layer equal to a length of said plurality of datablocks in said second layer.
 4. A two-layer optical disk, comprising:afirst layer of a disk-shaped recording medium for storing data; a secondlayer of a disk-shaped recording medium, positioned over said firstlayer, for storing data; a data block stored in said first layer, saiddata block having an interruption position; and an auxiliary data blockstored in said second layer, said data block in said first layer beinginterrupted at said interruption position during a reproduction toenable a selection between (i) inserting said auxiliary data block fromsaid second layer into said interruption position, and (ii) continuingsaid reproduction without insertion of said auxiliary data block intosaid interruption position.
 5. A method for reproducing a two-layeroptical disk having a first layer of a disk shaped recording medium forstoring data, a second layer of the disk shaped recording medium that ispositioned over the first layer for storing data, a data block beingstored in the first layer, the data block having an interruptionposition, and an auxiliary data block that is stored in the secondlayer, the method comprising:reading the data block in the first layerup to the interruption position; and selecting between inserting theauxiliary data block from the second layer at the interruption position,and continuing the reading of the data block in the first layer withoutany insertion of the auxiliary data block from the second layer at theinterruption position, wherein when the auxiliary data is selected forinsertion at the interruption position, the auxiliary data block fromthe second layer is inserted at the interruption position, andthereafter reading of the data block in the first layer continues fromthe interruption position, and when the continuing of the reading of thedata block in the first layer is selected, reading of the data block inthe first layer continues without insertion of the auxiliary data fromthe second layer.
 6. The two-layer optical disk of claim 1, wherein saidfirst layer and said second layer comprise films of dissimilarmaterials.
 7. The two-layer optical disk of claim 1, wherein said firstlayer is a film of aluminum, and said second layer is a film of gold. 8.The two-layer optical disk of claim 2, wherein said first layer and saidsecond layer comprise films of dissimilar materials.
 9. The two-layeroptical disk of claim 2, wherein said first layer is a film of aluminum,and said second layer is a film of gold.
 10. The two-layer optical diskof claim 3, wherein said first layer and said second layer comprisefilms of dissimilar materials.
 11. The two-layer optical disk of claim3, wherein said first layer is a film of aluminum, and said second layeris a film of gold.
 12. The two-layer optical disk of claim 4, whereinsaid first layer and said second layer comprise films of dissimilarmaterials.
 13. The two-layer optical disk of claim 4, wherein said firstlayer is a film of aluminum, and said second layer is a film of gold.14. The method of claim 5, wherein the first layer and the second layerare produced from dissimilar films.
 15. The method of claim 5, whereinthe first layer is produced from a film of aluminum, and the secondlayer is produced from a film of gold.